Hickory Grove Lake IA 03-SSK-950
Story County S24T83NR22W 2.5 mi SW of Colo.
- Assessment Cycle
- 2022
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 12/27/2021 10:20:35 AM
- Updated
- 1/5/2022 10:43:36 AM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2016 | Class A1 | Algal Growth: Chlorophyll a | Ambient monitoring: Iowa DNR-lakes | New data: WQ improvement (chemical / physical / bacterial) |
Assessment Summary
The Class A1 use was assessed as “not supported” due to levels of indicator bacteria that exceeded Iowa’s water quality standard and aesthetically objectionable conditions caused by non-algal turbidity. The Class BLW use was assessed (monitored) as “fully supported.” The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data. Note: A TMDL for indicator bacteria E. coli at Hickory Grove Lake was prepared by DNR and approved by EPA in June 2020. Because not all of the section 303(d) impairments identified for the current assessment/listing cycle (Turbidity) are addressed in the TMDL. This waterbody remains in Category 5a (impaired; TMDL required) for the current assessment/listing cycle.
Assessment Explanation
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2016-2018 22850001 Hickory Grove Lake
(maximum water depth) Iowa DNR 6 FT See Below 302 Hickory Grove Lake Hickory Grove Park Class A1 - Indicator Bacteria: No Data. See previous
assessments. Class A1 - pH: Site ID Data Source ID # Samples / # Years Minimum Value Maximum Value Mean Value # Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 22850001 6 9 / 3 7.4 8.7 8.2 0 3 NO Evaluated Full Class A1 - Lake TSI's: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Median Value Median TSI Violation? Assessment Type Support Level 22850001 6 Chlorophyll a TSI 9 / 3 36 66 58 NO Monitored Full 22850001 6 Secchi TSI 9 / 3 40 70 65 YES Monitored Not 22850001 6 Total Phosphorus TSI 9 / 3 44 85 63 NA NA NA 22850001 6 Inorganic suspended solids 9 / 3 0.6 10 3 NA NA NA DNR's assessment methodology indicates that at least two
assessment/listing cycles with a TSI value less than or equal to 63 are
necessary to suggest de-listing of an impairment. The chlorophyll a
TSI value for the 2016 assessment listing cycle was 65, which based on DNR's
assessment/listing methodology indicated an impairment based on the narrative
criteria protecting against aesthetically objectionable conditions. Because the
TSI value for the 2020 assessment/listing cycle was less than the trigger of 65
(2020 listing for chlorophyll a was 60), and because the TSI value for the
current listing cycle is also 58, based on DNR's methodology, these values
suggest "full support" of the Class A1 uses protecting against
aesthetically objectionable conditions and the impairment (5a) for chlorophyll
a is suggested for delisting for the 2022 assessment/listing cycle. Class BLW - Conventional Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Mean Value # Violations # Acute / Chronic Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 22850001 6 Ammonia 9 / 3 0.0003 0.135 0.06 NA 0 / 0 3 NO Evaluated Full 22850001 6 Dissolved Oxygen 9 / 3 3.6 11.6 9.3 1 NA / NA 3 NO Evaluated Full 22850001 6 pH 9 / 3 7.4 8.7 8.2 0 NA / NA 3 NO Evaluated Full 22850001 6 Temperature 9 / 3 19.8 28 23.6 0 NA / NA 3 NO Evaluated Full Class BLW - Lake Planktonic Cyanobacteria: Site ID Data Source ID # Samples Maximum Cyanobacteria Wet Mass Maximum Cyanobacteria % Composition Median Cyanobacteria Wet Mass Median Cyanobacteria % Composition Median Cyanobacteria Concentration = 75th Percentile Assessment Type Support Level 22850001 6 5 54.47 95.8% 4.65 29.9% NO Evaluated NA Class HH - Fish
Tissue Sampling: Site ID Biopart Year Species # in sample / # of samples Avg Length (cm) (Avg) Hg (ppm) Chlordane (ppm) Sum PCBs (ppm) 302 fillet 2013 channel catfish 5 45 0.09 <0.2 <0.6 302 tissue plug 2013 largemouth bass 5 32.9 0.239
Support Level Full
Assessment Key Dates
| 6/20/2016 | Fixed Monitoring Start Date |
| 9/11/2018 | Fixed Monitoring End Date |
| 8/2/2013 | Fish Tissue Monitoring |
| 9/16/2013 | Fish Tissue Monitoring |
Methods
| 120 | Surveys of fish and game biologists/other professionals |
| 222 | Non-fixed-station monitoring (conventional during key seasons and flows) |
| 260 | Fish tissue analysis |
| 340 | Primary producer surveys (phytoplankton/periphyton/macrophyton) |
| 420 | Indicator bacteria monitoring |